Man...I'm gonna be soooo stressed if I ever have to talk Esperanto with someone who's NOT named Adam or Sofia
Makes you wonder why there isn't a "j" tacked on already since it is, by definition, plural.
It's like in Spanish. "Nuestro" means "our singular masculine thing" and "nuestros" means "our plural masculine things". The "nuestr" part means "we" own something, and the ending specifies. Similar in Esperanto. "Ilia" means "their singular thing" and "iliaj" means "their plural things".
The -j only refers to the plurality of the possessee, not of the possessor. Iliaj nomoj gets -j because they have 2 names. But if they're the possessors of only one thing, there is no -j, e.g. "Ilia patro estas Doktoro Zamenhof." (not *iliaj).
Basically man you plural the object and its adjective. Wait... does that mean Esperanto is a romance language? Because that's a rule in Romance languages.
No, Esperanto is not a Romance language, although Zamenhof did borrow certain grammatical elements from various European languages, including but not exclusive to the Romance languages.
I keep seeing Sofia and Sophia used interchangeably here in the comments, but Why can't I spell the English "ph" when translating a name that doesn't end in the Esperanto nominal ending?
I found that Duolingo sometimes accepts "Sophia" and sometimes not, so I have taken to keeping to "Sofia". However, "Sophia" is the normal spelling of the name in English.